Since the question was referencing an aviation weather product (links no longer functional), there is a contextual answer as well. The aircraft dispatcher for an airline flight must plan the flight according to FAA regulations, some of which apply to weather information. Only specific sources of weather observations and forecast products are authorized, and the "VALID" period must also be taken into account.
If I'm planning a flight that will depart at 1400Z and arrive at 1755Z, I am not authorized to use a forecast product that was issued at 00Z and is valid at 1800Z. Even though this forecast product was issued prior to me starting to plan the flight, and thus is possibly the "most recently published product available", the product was produced for a specific valid period - namely, from 1800Z onward. I would have to reference as different product that was "valid" during my scheduled flight window.